Coating for molds



106. COMPOSITIONS,

COATING 0R PLASTIC. 8a

UNITED; STATES .Cl0SS Reference PATENT time;

DANIEL H. MELOCHE, OF DETROIT, MICHIGAN, ASSIGNOR TO EARL HOLLEY, OF

DETROIT, MICHIGAN.

COATING FOR HOLDS.

No Drawing.

To all whom it may concern:

Be it known that I, DANIEL H. Mnnoonn, a citizen of the United States, residing at 3248 Fourth Avenue, Detroit, in the county of Wayne and State of Michi an, have invented certain new and use 1 Improvements in Coatings for Molds, of which the following is a specification.

This invention relates to an improved coating for the protection of the surface of metal molds exposed to molten metal. The specific object of this invention is to provide means whereby the sprues and other portions of the metal molds used in the production of non-ferrous castings may be protected from the erosive action of said nonferrous metals. Another object is to maintain the metal in the sprues molten so as to prevent piping in the casting.

The difliculty heretofore found when casting non-ferrous metals in molds, which are usually made of iron or steel, is that the non-ferrous metals attack the iron or steel molds and eventually destroy them, especially in the sprue and gates, there being quite a considerable chemical aflinity between the iron molds and the metals cast therein. I have discovered that the coatin to be described hereafter, acts as an e ective barrier against the molten metals and thus protects the iron molds so that the life of the iron molds is extended indefinitely. An-

other difiiculty is that piping or porosity results from the premature freezing of the sprue.

I have discovered that if finally ground fire cla be suspended in wate in which a 1 t e waterlass ils dissolvfidk; anidl i3) tlhis sus ensiona 1 e am lac ea e,t at thi mixture of dilute water 'glass, fire clay, and lampblack constitutes a very satisfactory wash, and a cheap cast iron mold so coated is superior to an expensive uncoated steel mold. In order to make this wash adhere to the molds it is only necessary that the molds be higher than 250 F., and that the temperature of the mold be maintained Application filed January 12, 1924. Serial 1570. 685,898.

'2 2 above that temperature during the coating period. This merely means that heat must be applied between each coat. By having the wash relativel thin a great number of coats are require and the greater the number of coats the more adherent and therefore the more resistant is the coating to the erosive action of the nonferrous metals cast in the molds.

Satisfactory results have been obtained by using a 10 0 saturated solution of sodium silicate in mil mm.

1011 an equa weight of finely ground fire cla and lam black. The proportion of fifi? c ay and lampblacE should be two parts of fire clay to one part of lampblack. This mixture, consisting of approximately 45% water, 5% SQdlllIIl silicate, 33%

E:fige clay 5 and 17% lamphlack', is the. thic est was that I use.

By increasing the quantity of water, wlthout increasing the proportions of the other elements, I obtain a thinner wa which is more satisfactory w en re ative y intricate molds have to be protected. For simple molds, such as a piston mold, and for protecting the sprue the percentages given above are satisfactory.

One advantage of protecting the sprue with this heat-insulating coating is that the metal in the sprue stays molten longer and thus feeds the casting, so as to fill up any cavities which would otherwise form due to contraction.

What I claim is:

1. A coating for protecting iron molds, consisting of an inert I'eilflCQQQ InSMiLgIJAg mate ri al m iged WIHI lam p bl a ck an a small parentage of soluble s1 cate acting as a binder only, for 6 amp ack and the refractory insulating coating.

2. A coating for semipermanent molds to be used for the production of non-ferrous 9 castings, consisting of fire clay, lampblack, and a heat-resisting adhesive.

3. An insulating refractory wash for coating semipermanent molds, consisting Exafciinei' of lampblack and fire clay suspended in water in which there is dissolved a small percentage of heat-resisting binder.

4. A metal mold for the production of 5 non-ferrous castings, said mold being lined with a smooth adherent coating of fire clay, iam black, and an inorganic heat-resisting 1n er.

5. A metal mold for the production of non-ferrous castings, said mold being lined 10 with a smooth adherent coating of fire clay and lampblack, together with a binder of soluble silicate.

In testimony whereof I afiix my signature.

DANIEL MELOCHE. 

